Molecular Biology of Renal Injury: Emphasis on the Role of the Renin-angiotensin System

The developments in molecular biology of the past decade have created a powerful technology with important, if not revolutionary, clinical applications. This review discusses the molecular biology of renal injury focusing on the renin-angiotensin system as a model, first considering the molecular physiology of the renin angiotensin system within the kidney and then considering its abnormalities in renal injury. All of the components of the renin-angiotensin system are present within the kidney and are involved in modulation of glomerular microcirculation, in proximal tubular reabsorptive function, in control of glomerular/tubular balance, in modulation of medullary blood flow, and in growth and repair of the renal tubule. A new understanding of these multiple roles of the renin-angiotensin system within the kidney is made feasible by combining physiological studies with techniques such as mRNA analysis (e.g., Northern and slot blots, in situ hybridization, and RNA protection assays), transgenic animal studies, transfection studies, and restriction fragment length polymorphism analysis. The ways in which such approaches have been used to examine the role of the renin-angiotensin system in acute renal failure, proteinuric states, renal hypertension, and diabetes mellitus are discussed.